1. Field of the Invention
The present invention relates to reassembling technology of a frame, and more particularly, to a Data Over Cable Service Interface Specifications (DOCSIS) frame reassembling apparatus and method in a cable modem including a plurality of receiving channels.
This work was supported by the IT R&D program of MIC/IITA [2006-S-019-02, The Development of Digital Cable Transmission and Receive System for 1 Gbps Downstream].
2. Description of Related Art
A current Data Over Cable Service Interface Specifications (hereinafter, referred to as DOCSIS) cable modem (CM) extracts a DOCSIS Media Access Control (MAC) frame of a variable length from received Motion Picture Experts Group 2-Transport Stream (MPEG2-TS) packets, and processes the DOCSIS MAC frame being loaded in specific compression format standard (for example, MPEG2-TS) packets of a 188-byte fixed length and being transported using a single receiving channel.
A method of loading the DOCSIS MAC frame of the variable length in the MPEG2-TS packets of the fixed length basically includes a 4-byte fixed header an optional 1-byte Point_field, and DOCSIS MAC frame data of a 183-byte or 184-byte length, and the 4-byte MPEG header follows an MPEG standard.
The DOCSIS MAC frame may start in any location of an MPEG2-TS packet payload, and may be included in a single MPEG2-TS packet or may be included over several MPEG2-TS packets based on a DOCSIS MAC frame length.
According to various DOCSIS MAC frame transport methods, the CM needs to extract the DOCSIS MAC frame from the received MPEG2-TS packets. The MPEG2-TS packet may be corrupted by a channel error.
Accordingly, the CM needs to delete the corrupted MPEG2-TS packet when detecting an MPEG2-TS packet error. In this case, loss of the DOCSIS MAC frame based on MPEG2-TS packet deletion needs to be minimized, and new DOCSIS MAC frames need to be extracted from the MPEG2-TS packets received after the MPEG2-TS packet error. In particular, the CM including a plurality of receiving channels needs to extract the DOCSIS frame classified by a channel and use a buffer classified by the channel in order to multiplex the DOCSIS frames among channels. A method of effectively controlling the buffer classified by the channel when the MPEG2-TS packet error occurs is required.